1. Field of the Invention
The present invention relates to a power amplifier circuit and a test apparatus. More particularly, the present invention relates to a power amplifier circuit that applies an output voltage according to a given input voltage to a load and a test apparatus that tests a device under test.
2. Related Art
FIG. 9 shows a power amplifier circuit 201, a phase compensation capacitor 202 connected to the power amplifier circuit 201, and a load 203. The power amplifier circuit 201 supplies an output voltage Vout according to a given input electric power Vin to the load 203 and supplies a power source current Iout according to electric current consumption of the load 203 to the load 203. The phase compensation capacitor 202 is connected between an output port of the power amplifier circuit 201 and a ground. The phase compensation capacitor 202 and an output resistor 204 of the power amplifier circuit 201 forms a filter circuit. This filter circuit performs phase compensation between the output voltage Vout and the input voltage Vin. According to this, the power amplifier circuit 201 can stably supply electric power to the load 203.
Meanwhile, when supplying a large current to the load 203, it is desirable to reduce the output resistor 204. However, when reducing the output resistor 204, it is necessary to increase capacitance of the phase compensation capacitor 202 to keep cut off frequency of the filter circuit. When the high-capacity phase compensation capacitor 202 is connected to the power amplifier circuit 201, an inrush current according to fluctuation of the output voltage Vout becomes large. Therefore, in such a case, a power source having sufficiently large current supply capability has to be connected to the power amplifier circuit 201 in consideration of an inrush current as well as an amount of power source current.